CIE Jun 2016 v2 Paper 4 Q7

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(a) Amino acids can be separated by electrophoresis. 14 PMT (i) Draw a labelled diagram of the apparatus used to separate a mixture by electrophoresis. (ii) Explain the principles of the separation of amino acids by electrophoresis.[2] [3] (b) Electrophoresis is usually carried out in a buffer solution. Given three buffers, with pH values of 2.0, 7.0 and 12.0, suggest, with a reason, which buffer would be the most suitable for the separation of the following amino acid mixtures. Your reasons should refer to the structure of each molecule. (The structures of these amino acids are given in the Data Booklet.) (i) Asp and Val buffer pHreason(ii) Lys and Ser buffer pHreason(iii) Tyr and Phe buffer pHreason[3]UCLES 2016 9701/42/M/J/16<br /> (c) (i) Draw the structure of the dipeptide Gly-Ser, showing the peptide bond in full. 15 PMT [2] The infra-red spectrum of Gly-Ser is shown below. 100 e c n a t t i m s n a r t 50 3000 0 4000 2000 1500 wavenumber / cm1 1000 500 (ii) Use the Data Booklet to identify the bond in the molecule of Gly-Ser that is responsible for each of the peaks indicated on the above infra-red spectrum. EFG[2] [Total: 12]UCLES 2016 9701/42/M/J/16 [Turn over<br />

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